Thermal deburring apparatus includes a mixing chamber in which gases which can be burned under explosive conditions, typically hydrogen and oxygen, are mixed and ignited, for example by a spark plug. The gases are conducted in the mixing chamber under controlled conditions, and then the mixing chamber must be isolated from the gas supply. The valves included in the gas supply which isolate the supply from the mixing chamber are subjected to extremes of operating conditions -- thermal as well as pressure shocks under extremely high temperature and pressure conditions. In one position of the valve, passage for gas from a supply to the mixing chamber is free; in another condition, however, gas flow is interrupted and, additionally, the valve must be capable of withstanding explosion pressure and reliably prevent backflash or backfire.
It has previously been proposed to provide a valve for a thermal deburring machine in which the gas inlet is sealed by a ball seat. The ball is held in sealing position by an external force. Such valves are subject to leakage since leaks develop at the seat of the ball, particularly due to contamination, dirt or the like; at the high loads -- regarding temperature as well as pressure -- any leaks, even small ones, rapidly lead to failure of the valves, and to interruption of proper operation of the entire system, since any areas of leakage or not absolute tightness, tend to wear rapidly upon operation of the deburring machine.